Researchers, medical professionals and others must frequently determine the presence and concentration of a large number of different types of microbial organisms, including viruses. Many qualitative and quantitative methods are known in the scientific arts. A number of these methods require either expensive equipment to analyze the test sample, analysis of the sample at a location remote from the sample collection location, or relatively long time periods to produce the result. By way of example, determining titer typically entails serial dilution of a sample followed by culturing, which may take several days. The process is tedious, time consuming and must be carried out in a controlled laboratory environment.
As another example, Coulter counters are frequently used to detect and quantitate microbial organisms by measuring changes in electrical conductance of a small aperture as fluid containing the organisms is drawn through. The solution being studied is drawn with a vacuum pump through an electrically charged tube with a tiny hole at one end. As it passes through the hole, each particle within the solution blocks the electrical field for a moment. Distortions in voltage can be matched to specific types and numbers of particles. One substantial disadvantage of existing Coulter counters is their low throughput efficiency, which substantially extends measurement times. Coulter counting measurement relies on particles passing through a tiny orifice (microchannel) one by one from one chamber to the other. Thus, in order to complete sampling of a small number of particle solutions, thousands of micro or nanoparticles have to pass through the orifice one by one, which could be prohibitively time consuming. As another disadvantage, the equipment is costly. Furthermore, while the Coulter counter is effective for counting prokaryotic (bacterial) cells, it is not useful for counting virus because of their much smaller size.
As yet another example, some methods determine the presence of an analyte, but provide no information about the concentration. Illustratively, the “presence/absence” format of bacterial testing, such as in the Colilert® chemical mixture (IDEXX, Laboratories, ME) test, detects the presence of the targeted organism (e.g., fecal coliforms) but give no idea as to microbe concentrations. Colilert® also requires incubation in test water for 24 hours before results can be obtained.
What is needed is a simple, cost effective and reliable system and method for detecting a wide range of microbial organisms, including virus, and determining concentrations in near real-time to determine titer, without the requirement to grow micro-organisms. The invention is directed to overcoming one or more of the problems and solving one or more of the needs as set forth above.